The authors study the demographic characteristics of Montreal's French-Canadian Catholic, Anglo-Protestant and Irish Catholic citizens from the 1840s to the end of the nineteenth century. To trace the evolution of the population, the authors collected all baptisms, marriages, deaths and nominal census entries for twelve sample surnames from the three groups. The sample permitted the matching, chaining, and full reconstruction of several hundred families representative of each the city's three principal cultural communities. The authors conclude that the three communities functioned as distinctive subsystems, each with its own age structure, vital rates, and behavioral patterns and strategies.